Clojure 1.3.0-alpha4
user=> (defn f [r] (dosync (println "Start" @r) (Thread/sleep 6000) (println "End" @r)))
#'user/f
user=> (def r (ref 1))
#'user/r
user=> (do (.start (Thread. #(f r))) (dosync (ref-set r 5)))
Start 1
5
user=>
Start 5
End 5